Who is it that you're afraid of getting caught by? Your mother, or the authorities? Most people who ask this question (how to grow without the parents finding out) get the same answer: don't do it. It's almost impossible to conceal the smell without specialized equipment...equipment that simply isn't easy for a minor to acquire. Assuming that you are a minor, that is.

Storm & Opie summed up the rest pretty nicely. If you plan on going outside with your grow, you'll need to wait. Cooler weather & shorter days are on their way. This'll give you plenty of time to educate yourself on the finer points of growing. Talk to your mother about your options, but also remember to educate yourself heavily about the current laws regarding cultivation. If things go sour, you're probably looking at federal penalties...not just a slap on the wrist and subsequent probation/fines.

If you decide that you want to pursue this lifestyle (not hobby) further, then consult forums like these to discover what the possibilities are.